Trane BAS-SVP10A-EN Thermostat User Manual


 
BAS-SVP10A-EN 25
Wiring Requirements for Communicating Thermostats
BACnet networks use a daisy chain configuration. A daisy chain means that there is only one main
cable and every network device is connected directly along its path.
Figure 2 illustrates two improper network configurations and theproper daisy chain configuration.
Figure 2. Incorrect and correct network configurations
BACnet MS/TP Link Wiring
BACnet MS/TP link wiring must be field-supplied and installed in compliance with the National
Electric Code (NEC) and local codes.
BACnet Configuration Requirements
Follow these configuration requirements:
BACnet wiring must use daisy-chain configuration. Maximum length is 4,000 ft (1219 m).
BACnet links are polarity sensitive; consistent wiring polarity must be maintained between
devices.
Limit each link to 30 controllers or 60 total controllers per Tracer SC.
BACnet Wiring Best Practices
The following wiring practices are recommended:
Use 18 AWG, (24 pF/ft. max.), shielded, twisted pair communication wire (Trane purple wire).
Strip no more than 2 in. (5 cm) of the outer conductor of shielded wire.
Avoid sharing 24 Vac power between unit controllers.
Ensure that 24 Vac power supplies are consistently grounded. If grounds are not maintained,
intermittent or failed communication could result.
Connect the shield portion of the communication wire at the first unit controller in the link.
Use a Tracer BACnet terminator at each end of the link.
For additional best practices, see the Unit Controller Wiring Guide For the Tracer SC™ System
Controller (BAS-SVN03x-EN).